1. Field of the Invention
This invention relates to stringed musical instruments. In particular, the invention relates to a stringed musical instrument with embedded digital signal processing (DSP) modeling capabilities to model an acoustic stringed instrument.
2. Description of Related Art
Stringed instruments utilize vibrating strings to generate tones, and therefore music, since notes of music are merely particular tones. More particularly, a tone or note is a sound that repeats at a certain specific frequency. Throughout the world, various cultures have created a multitude of different stringed instruments such as: guitars, mandolins, banjos, basses, violins, sitars, ukuleles, etc., to create music. Moreover, with the advent of electronics, many of these stringed instruments have now been electrified to operate in conjunction with an amplifier and speaker. One of the most common stringed instruments in use today is the guitar—in both its electric and acoustic forms. The guitar is one of the most popular musical instruments in use today, and it spans a huge range of musical styles—e.g. rock, country, jazz, folk, etc.
As previously discussed, the vibrating string of a stringed instrument generates a musical tone or note, which is in turn a function of: the length of the string; the amount of tension on the string; the weight of the string; the shape and thickness of the body of the stringed instrument, etc. Generally, stringed instruments, and the guitar in particular, include a body having a bridge to which each of the strings are respectively mounted, a neck having frets and a nut or ‘zero’ fret, and a head having tuning pegs to which each of the strings are also respectively mounted. The length of the string is the distance between the bridge and the nut or ‘zero’ fret. The amount of tension on the string is determined by the winding of the tuning peg, which tightens and loosens the string (i.e. imparting tension) in order to tune the string to a certain note. In playing a stringed instrument, when a musician presses down on a string at a fret, the length of the string is changed and therefore its frequency is changed as well. The frets are spaced out so that the proper frequencies are produced when a string is held down at a given fret (and therefore the proper note is produced). However, it should be appreciated that not all stringed instruments have frets.
Looking at electrical stringed instruments, and utilizing an electric guitar as a particular example, to produce sound an electric guitar electronically senses the vibration of a string and generates an associated electrical signal and then routes the associated electric signal to an amplifier. The sensing generally occurs by utilizing electromagnetic pickups mounted under each of the strings of the guitar, respectively, in the guitars' body and neck, at different locations. These electromagnetic pickups typically consist of a bar magnet wrapped with a coil of thousands of turns of fine wire. The vibrating steel strings of the electric guitar produce a corresponding vibration in the magnetic field of the electromagnetic pickup and therefore a current in the coil. This current represents the sound of the string at the location of the pickup and can be routed to an amplifier. Many electric guitars have two or three different magnetic pickups located at different points of the body and neck. Each magnetic pickup will have a distinctive sound, and multiple pickups can be paired, either in-phase or out, to produce additional variations. Thus, the electromagnetic pickup locations for particular types of electric guitars are a major factor in determining the “sound” associated with the particular electric guitar along with other factors. For example, classic “sounds” are associated with various types of GIBSON and FENDER brand electric guitars, as well as others.
In order to achieve a diverse array of well-known or classic types of guitar tones, a guitarist has traditionally been required to use many different guitars. Previous attempts have been made to allow a guitarist to obtain many different classic guitar sounds utilizing only one guitar, however, these attempts generally require modification of the guitar, non-standard guitar cabling, and extra equipment. For example, previous attempts have been made to emulate the different sounds of various guitars by processing the individual strings of a guitar by means of a multi-phonic pickup attached to a standard electric guitar that delivers string vibration signals to a separate outboard processing unit that utilizes digital signal processing (DSP) techniques. The processing unit performs DSP algorithms on the string vibration signal to simulate the sound of a particular well-known guitar. Unfortunately, this requires modification to the standard electric guitar, the use of non-standard guitar cables, and the use of a detached processing unit away from the guitar, between the guitar and the amplification system.
Moreover, previous DSP techniques, which are utilized to emulate the locations of the electromagnetic pickups along the string for the desired electric guitar to be emulated, are inadequate. This is because these DSP algorithms only emulate the electromagnetic pickups in one-dimension, in the horizontal ‘x’ axis along the length of the string utilizing simplistic modeling techniques. Further, the simplistic algorithms utilized completely ignore a critical aspect of the tone produced by an electromagnetic pickup, which is its distance from the string in the vertical or ‘y’ axis, referred to as the “pickup height”. Thus, previous modeling techniques are insufficient to truly emulate the overall tone of the guitar in response to a string vibration signal, and therefore cannot truly emulate the sound of the desired classic electric guitar, or any desired electric string instrument to be emulated for that matter.
Looking at acoustic stringed instruments, and utilizing an acoustic guitar as a particular example, presently, in order to re-create desired acoustic guitar sounds, a guitarist may use an acoustic guitar with a variety of differing microphone set-ups, transducer pickups, preamps, and signal processing equipment in order to provide very rough approximations of desired classic acoustic guitar sounds.
Further, as with electric guitars, previous attempts have been made to emulate the different sounds of various acoustic guitars by processing the individual strings of an acoustic guitar by means of a multi-phonic pickup attached to a standard acoustic guitar that delivers string vibration signals to a separate outboard processing unit that utilizes digital signal processing (DSP) techniques. The processing unit performs DSP algorithms on the string vibration signal to simulate the sound of a particular well-known acoustic guitar. Unfortunately, this requires modification to the standard acoustic guitar, the use of non-standard guitar cables, and the use of a detached processing unit away from the acoustic guitar, between the acoustic guitar and the amplification system.
More particularly, looking at sound creation fundamentals in an acoustic stringed instrument, and utilizing an acoustic guitar as a particular example, generally, an acoustic guitar produces sound by the vibration of a string of an acoustic guitar being naturally amplified acoustically by vibration-reinforcement mechanisms defined by the acoustic guitar's design and construction. Along with other factors, these vibration-reinforcement mechanisms generally include an acoustic guitar's materials, construction, size, shape, sound-board characteristics, and type of strings used. All of these constitute major factors in determining the “sound” associated with a particular acoustic guitar.
When playing an acoustic guitar in a strictly acoustic environment (with no electronics involved) the natural occurrence of the sound produces the desired result for the guitarist. However, in order to record an acoustic guitar, or to amplify an acoustic guitar for live performance, it is typically necessary to utilize an electronic means of capturing and reproducing the acoustic signal.
For recording and/or amplification, a microphone is the most commonly used device that can faithfully capture the output of an acoustic guitar, provided no other ambient noise is present and acoustic reflections from the instrument's surroundings are not sufficient as to alter the desired acoustic result.
In a live performance, the sound captured electronically needs to be amplified and played through loudspeakers for an audience to hear. One of the difficulties in a live acoustic guitar performance is producing sufficient volume without producing “feedback.” If sound energy from the loudspeakers appears at the microphone with sufficient volume, then “feedback” from the signal will return to the microphone, which results in an undesirable and annoying audible sound.
Consequently, attempts have been made to capture an acoustic stringed instrument's sound with special microphones or piezoelectric devices that are acoustically coupled to the bridge or body of the acoustic stringed instrument. Although this approach allows for a higher level of amplification before feedback occurs, it fails to capture many of the important acoustic properties of the acoustic stringed instrument, such as an acoustic guitar, thus resulting in an amplified acoustic guitar sound that no longer resembles the actual acoustic guitar's sound.